The invention relates to continuously operating filmstrip developing machines of the type comprised of processing fluid stages and drying stages arranged one after the other, with the filmstrips being guided through the successive stages in a winding path. Typically, the speed of travel of the film is determined by a film-pulling roller.
Considerable progress has been made in recent years in the processing of amateur still photographs, the developing and copying processes employed having been automated to a very great extent. A considerable number of automatically operating processing devices have been devised, such as copying devices, cutting devices, notching devices, developing devices, and the like. It has not in general been possible to automate to a similar extent the developing of exposed amateur still filmstrips, even though it is well known to develop and dry motion-picture film in continuously operating machines. Instead, it has in general continued to be the practice to develop filmstrips received from individual customers in so-called hanger machines employing dipping methods.
In order to be able to develop individual film strips in a continuously performed process, it is necessary to in some manner connect the filmstrips together. In this connection an important problem is the forming of splices which will not come apart in the individual baths of developer, fixer and bleaching fluids and which furthermore are capable of withstanding the mechanical stresses to which they will be subjected in passing through a continuously operating developing machine. When employing a continuous development method, each filmstrip must be guided through from ten to twenty, or even more, processing fluid stages, and then through one or more drying stages. In each of these stages, the filmstrip travels about a plurality of rollers. In order to be able to feed the assemblage of spliced-together filmstrips into film guide arrangements of conventional construction, various proposals have been made relative to the manner in which the film should be fed in order to reduce the stresses leading to film tears.
For example, Federal Republic of Germany Offenlegungsschrift No. 1,962,856 discloses a continuously operating developing machine in which a film-pulling roller is located intermediate the processing fluid stages of the machine, on the one hand, and the drying section of the machine, on the other hand. The film-pulling roller of that machine can be driven at different speeds. This main transport roller (pacer), serving both to determine the filmstrip tension and the speed of film transport, is in conventional machines always arranged between the processing fluid and drying stages of the machine. In this way, the main transport roller additionally serves to compensate for or equalize the differing filmstrip tensions as between the processing fluid stages of the machine, on the one hand, and the drying stages of the machine, on the other hand.
This known arrangement of the film-pulling roller is characterized by a number of disadvantages. When located intermediate the wet-treatment and drying stages of the machine, the pulling roller must have a very large diameter or else slippage of the film strip cannot be reliably enough avoided. Also, means must be provided within the one or more drying stages located downstream of the film-pulling roller for driving the film through the drying part of the developing machine, and these additional means involve further expense. If different photographic materials are to be processed, then it has proved to be necessary to so construct the film-pulling roller as to make it of variable diameter, because changes in filmstrip breadth can result in the development of stresses leading to filmstrip tearing. Additionally, even a small wearing away of the surface of the film-pulling roller, for example to the extent of a few microns, can lead to a loss of correspondence between the pulling force exerted by the roller and the other stresses to which the filmstrip is subjected, resulting in tearing of the filmstrip.